X-ray imaging systems have become a valuable tool in medical applications such as for the diagnosis of many diseases. As standard screening for breast cancer mammography, for example, two-dimensional (2D) x-ray images are taken across the entire breast tissue. These 2D mammograms are limited by tissue superimposition. That is, lesions may be masked by the tissue above or underneath them, and/or normal tissue structures may mimic appearance and/or behavior of a lesion in the 2D image data. In order to minimize limitations of standard 2D-mammography caused by tissue superimposition, digital breast tomosynthesis using digital receptors has been developed.
Digital tomosynthesis systems employ at least one x-ray tube, which is moved in a trajectory (e.g., an arc, line segment, circle, other trajectory) above a detector (e.g., stationary, movable such as to remain perpendicular and/or within an angular range of a line passing through a focal spot for the imaging system, etc.). In digital breast tomosynthesis (DBT), the volume information of an object of interest can be derived from a series of images, known as projection images or projections, which are taken at various angles using one or more x-ray sources. Objects of different heights in a breast display differently in the different projections. From the 2D projection images, three-dimensional (3D) volumes can be generated for review. The generated 3D volume portions offer advantages to overcome the limitations associated with tissue superimposition. During the adoption period of the tomosynthesis technology, the provision of the 2D mammography is still desired by the medical professional or radiologist, who wants to use existing expertise gained from reviewing 2D mammograms. Furthermore, archived 2D mammograms can be better compared with images obtained using the same technology than with images obtained using exclusively a new modality such as tomosynthesis.
To address the need for 2D mammograms besides the provision of the relatively recent tomosynthesis images, a combination acquisition of images can be performed. That is, both the known 2D mammography and digital breast tomosynthesis projections are acquired for the same object of interest. However, since the average dose from tomosynthesis imaging is approximately the same as the known mammogram 2D imaging, the radiation exposure is roughly doubled. Thus, there is a need to generate or acquire the information of known 2D mammograms without performing two examinations, in order to reduce the dose. There is a need for more accurate analysis of image information to generate a synthetic 2D image from the reconstructed DBT volume and/or the set of projections, for example.
Computer-aided diagnosis (CAD) can assist a healthcare practitioner in interpreting medical images. Using CAD, 3D volumes, 2D images, etc., can be processed to highlight suspicious areas of an image to offer input to support a decision made by the healthcare practitioner. There is a need for improved CAD to improve assistance to the healthcare practitioner for improved diagnosis and treatment of patients.